origin + microseconds(lrint((out_pts - out_pts_origin) * 1e6 / TIMEBASE));
int64_t in_pts = lrint(in_pts_origin + TIMEBASE * frameno * speed / output_framerate);
pts = lrint(out_pts);
origin + microseconds(lrint((out_pts - out_pts_origin) * 1e6 / TIMEBASE));
int64_t in_pts = lrint(in_pts_origin + TIMEBASE * frameno * speed / output_framerate);
pts = lrint(out_pts);